1. Field of the Invention
The present invention relates to copper precursor compositions and their synthesis, and to a method for production of copper circuits in microelectronic device structures, as for example in formation of metal interconnects for the manufacture of semiconductor integrated circuits, thin-film recording heads and packaging components, or otherwise for metallizing or forming copper-containing films on a substrate by metalorganic chemical vapor deposition (MOCVD) utilizing such precursor compositions. The precursor compositions of the invention are also usefully employed for forming seed layers of copper for subsequent electroless or electrochemical plating of copper and other metals.
2. Description of the Related Art
As a result of its low resistivity, low contact resistance, and ability to enhance device performance through the reduction of RC time delays, copper has emerged as a preferred metal for metallization of VLSI devices. Copper metallization has been adopted by many semiconductor device manufacturers for production of microelectronic chips, thin-film recording heads and packaging components.
Chemical vapor deposition (CVD) of copper provides uniform coverage for the metallization. Liquid CVD precursors and/or solid precursors dissolved into solvents or excess ligands enable direct injection and/or the liquid delivery of precursors into a CVD vaporizer unit. The accurate and precise delivery rate can be obtained through volumetric metering to achieve reproducibility during CVD metallization of a VLSI device.
Currently only a few liquid copper precursors are commercially available. These include (hfac)Cu(MHY), (hfac)Cu(3-hexyne), (hfac)Cu(DMCOD) and (hfac)Cu(VTMS), wherein hfac=1,1,1,5,5,5-hexafluoroacetylacetonato, MHY=2-methyl-1-hexen-3-yne, DMCOD=dimethylcyclooctadiene, and VTMS=vinyltrimethylsilane.
Various copper precursors useful for MOCVD of copper interconnects in semiconductor integrated circuits are described in U.S. Pat. Nos. 5,085,731; 5,098,516; 5,144,049; and 5,322,712; and the references cited in those patents. New and useful compositions and processes for the production of copper that improve on, or provide alternatives to, these known compositions would be highly desirable and embody a significant advance in the art.
With respect to the copper precursors that have come into use for copper MOCVD metallization, there are concerns associated with using (hfac)CuL precursors, where hfac=1,1,1,5,5,5-hexafluoroacetylacetonate and L=neutral Lewis base ligands. Copper metallization in integrated circuit manufacture typically utilizes a barrier layer between the copper layer and the underlying structure in order to prevent detrimental effects that may be caused by the interaction of a copper layer with other portions of the integrated circuit. A wide range of barrier materials is conventionally utilized, including materials comprising metals, metal nitrides, metal silicides, and metal silicon nitrides. Exemplary barrier materials include titanium nitride, titanium silicide, tantalum nitride, tantalum silicide, tantalum silicon nitrides, niobium nitrides, niobium silicon nitrides, tungsten nitride, and tungsten silicide. In instances where (hfac)CuL type precursors are used for copper metallization, interfacial layers are formed between the barrier layer and the copper layer. These interfacial layers cause the metallization to have poor adhesion and high contact resistivity.
The deficiencies of inferior adhesion and excessively high contact resistivity incident to formation of interfacial layers when using (hfac)CuL copper precursors has been attributed to the hfac ligand, which contains both oxygen and fluorine. To overcome such deficiencies, it would be a significant advance in the art to provide copper MOCVD precursors having a reduced oxy/fluoro content. It would be particularly advantageous to provide copper MOCVD precursors of an oxygen-free character.
It is accordingly an object of the present invention to provide a new class of anoxic (oxygen-free) copper precursors and formulations.
It is another object of the invention to provide methods of forming copper in the manufacturing of integrated circuits and other microelectronic device structures using such precursors and formulations.
It is a further object of the invention to provide metallization technology for forming interconnects and other device structures that overcome the shortcomings and limitations of the prior art, including improved adhesion, improved contact resistances, improved film resistivities and improved device integration.
It is another object of the invention to provide a method of metallizing or forming copper-containing films on a substrate by metalorganic chemical vapor deposition (MOCVD) utilizing such novel copper precursor compositions and formulations.
It is a further object of the invention to provide adherent thin-films for seeding electroless and/or electrochemical plating solutions and to overcome the shortcomings and limitations of the prior art, including improved adhesion, improved contact resistances, improved films resistivities, improved plating, improved conformality, improved manufacturing, and improved device integration.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.
The present invention relates generally to copper pyrazolate compositions, which are advantageously of an oxygen-free character, useful as source reagents for forming copper on substrates, and to methods of making and using such compositions.
In one aspect, the invention relates to a composition useful for the production of copper by chemical vapor deposition, comprising one or more pyrazolate copper (I) Lewis base adduct(s).
In a particular aspect, the invention relates to a copper precursor of the formula (RRxe2x80x2Rxe2x80x3)PzCuL, wherein (RRxe2x80x2Rxe2x80x3)Pz is a pyrazolyl moiety of the formula: 
wherein R, Rxe2x80x2 and Rxe2x80x3 are independently the same as or different from one another and each of R, Rxe2x80x2 and Rxe2x80x3 is independently selected from H, C6-C10 aryl, C6-C10 fluoroaryl, C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 perfluoroalkyl, and C3-C6 cycloalkyl, with the proviso that at least one R contains fluorine; and L is a neutral Lewis base ligand, such as a neutral Lewis base alkene, alkyne or diene.
A further aspect of the invention relates to pyrazolate copper (I) Lewis base adducts that are devoid of oxygen constituents therein.
Another aspect of the invention relates to specific copper precursor formulations useful for liquid delivery metalorganic chemical vapor deposition of copper, comprising:
(a) a precursor composition selected from the group consisting of:
(i) pyrazolate copper (I) compounds; and
(ii) pyrazolate copper (I) neutral Lewis base adducts; and
(b) a solvent composition for the precursor composition.
A further aspect of the invention relates to copper precursor formulations useful for liquid delivery metalorganic chemical vapor deposition of copper, comprising:
(a) a precursor composition selected from the group consisting of:
(i) (RRxe2x80x2Rxe2x80x3)PzCu wherein: Pz is a pyrazolyl moiety and R, Rxe2x80x2 and Rxe2x80x3 are independently the same as or different from one another and each of R, Rxe2x80x2 and Rxe2x80x3 is independently selected from H, C6-C10 aryl, C6-C10 fluoroaryl, C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 perfluoroalkyl, and C3-C6 cycloalkyl;
(ii) (RRxe2x80x2Rxe2x80x3)PzCuL wherein: Pz is a pyrazolyl moiety and R, Rxe2x80x2 and Rxe2x80x3 are independently the same as or different from one another and each of R, Rxe2x80x2 and Rxe2x80x3 is independently selected from H, C6-C10 aryl, C6-C10 fluoroaryl, C1-C6 alkyl, C1-C6 fluoroalkyl, C3-C6 perfluoroalkyl, and C1-C6 cycloalkyl, with the proviso that at least one R contains fluorine; and L is a Lewis base ligand, such as an amine or a neutral Lewis base alkene, alkyne, or diene; and
(b) a solvent composition for the precursor composition.
A further aspect of the invention relates to pyrazolate copper (I) precursor formulations that are devoid of oxygen constituents therein.
Another aspect of the invention relates to specific copper precursors such as [(CF3)2PzCu]3, (CF3)2PzCu(3-hexyne), and (CF3)2PzCu[bis(tms)acetylene], wherein Pz is a pyrazolyl moiety and tms is trimethylsilyl.
In further aspects, the invention variously relates to: a process useful for the production of copper, in which a composition of the above-described type is subjected to chemical vapor deposition; a process of forming a seed layer by liquid injection or direct vaporization of a composition of the above-described type; copper made by the process of subjecting to chemical vapor deposition a composition of such type; and integrated circuits made using such process.
A further aspect of the invention relates to a process for synthesizing a copper precursor, including reacting (RRxe2x80x2Rxe2x80x3)pyrazole starting material with a stoichiometric excess of Cu2O, and recovering (R,Rxe2x80x2Rxe2x80x3)pyrazolyl copper from the reaction, optionally followed by reacting the (R,Rxe2x80x2Rxe2x80x3)pyrazolyl copper with a neutral Lewis base compound, to yield a (R,Rxe2x80x2Rxe2x80x3)pyrazolyl copper Lewis base adduct. The Lewis base adducted pyrazolate copper complexes exhibit higher solubility in organic solvents. Such high solubility is particularly advantageous in making solution compositions using the solid complexes.
A still further aspect of the invention relates to a process for synthesizing a copper precursor, including reacting bis(trifluoromethyl)pyrazole with a stoichiometric excess of Cu2O, and recovering bis(trifluoromethyl)pyrazolyl copper from the reaction, optionally followed by reacting the bis(trifluoromethyl)pyrazolyl copper with a neutral Lewis base compound, to yield a bis(trifluoromethyl)pyrazolyl copper Lewis base adduct. Another aspect of the invention relates to a process for synthesizing the (RRxe2x80x2Rxe2x80x3)pyrazolyl copper Lewis base adduct directly from the Lewis base in the presence of Cu2O and (RRxe2x80x2Rxe2x80x3)pyrazole starting material.
Yet another aspect of the invention relates to a method of depositing copper on a substrate, comprising volatilizing a copper precursor composition of the present invention, to form a precursor vapor and contacting the precursor vapor with the substrate under elevated temperature vapor decomposition conditions to deposit copper on the substrate.
The precursor compositions of the invention are useful for the manufacture of copper, including copper interconnects for integrated circuits, thin-film recording heads and/or packaging components.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.